The present invention relates to a recording and/or reproducing device capable of accessing a desired data track on an information medium; and more particularly an improvement of a device capable of switching between two searching modes, one being the rough searching mode in which recording and/or reproducing transducer means can be displaced at a high velocity to the vicinity of a desired data track and the other being the fine searching mode which follows the rough searching mode and in which the transducer means is displaced at a relatively slow velocity so as to be correctly positioned on the desired data track.
The recording and/or reproducing device of the type described comprises in combination transducer means for writing and/or reading data onto or out of one of a plurality of data tracks on an information medium, first driving means for displacing the transducer means in the direction substantially perpendicular to the direction of the tracks on the information medium for searching a desired data track, a second driving means for displacing both the transducer means and the first driving means in the direction substantially perpendicular to the direction of the tracks on the information medium for effecting the rough searching, and tracking control means for controlling the first driving means in such a way that scanning means of the transducer means may be always positioned on the proper track.
Each of the data tracks on the information medium is labeled with a specific address and searching for a desired data track is based upon such addresses. In the case of the searching, first, the tracking control means is rendered inoperative and the second driving means is energized to displace the transducer means to the vicinity of a desired data track. Thereafter the transducer means is displaced in the fine searching mode by the first driving means. Thus, the transducer means traverses the tracks until it can finally access a desired data track.
In the data track searching device of the type described, when the transducer means is displaced at a high velocity in the rough searching mode by the second driving means, the first driving means is shifted or deviated due to inertia. As a result, when the transducer means is brought to the vicinity of a desired data track and the tracking control means is enabled, unstable draw-in of the control system occurs so that it takes an undesirably long time before the control system is completely stabilized. Furthermore, it happens very often that when the tracking control means is enabled, the transducer means is not drawn in the track on which the transducer means is positioned but is drawn into a track spaced away from the former. As a result, the search time becomes longer.
There has been also devised and demonstrated a method in which the displacement of the transducer means is detected by detecting the number of tracks which the transducer has traversed, whereby the position of the transducer means is determined. However, in this case, if the first driving means is shifted or deviated, a normal signal is not applied to the transducer means so that the position of the transducer means cannot be accurately determined. As a result, the search time also becomes longer.